A touch panel or screen is one of the major interfaces between human and machine in modern mobile device. A mobile device may be used outdoor or in damp place, so it may be touched with water or other conductive liquid on the touch panel or screen. Random size and shape of the conductive liquid causes problematic uncertainties when detecting the real touches.
In the conventional mutual capacitance touch panel technology, part of charges from the driving voltage will be taken away when external conductive object such as a finger or a stylus approximates or touches the touch panel or screen. It causes the measured voltage on the sensing electrodes drop. However, the random sized and shaped conductive liquid does not connect to the ground. In some cases, the conductive liquid causes the measured voltage on the sensing electrode to rise, which is different from effects caused by a finger. In another cases, the conductive liquid causes the measured voltage on the sensing electrode drop, which can be mistaken to be an external conductive object.
Above all, a touch sensitive method and device for distinguishing the conductive liquid from the external conductive object is needed.